Evaluation of the Mechanical Properties of 3D Printed Splint Material

Objectives: To evaluate the effect that polymerization methods have on the mechanical properties of a light-curing methacrylate based resin material (IMPRIMO^® LC Splint), used for the fabrication of 3D printed occlusal splints and surgical guides.
Methods: Ninety-six bar-shaped specimens were 3D-printed (Asiga MAX), half of them with a layer thickness of 100 µm (Group A), and half with 50 µm (Group B). Each group was divided into 3 subgroups: Subgroup I where the specimens were post-cured in a light emitting diode (LED) unit without nitrogen. In Subgroup II the specimens were LED post-cured with nitrogen to prevent the oxygen inhibition layer. In subgroup III the specimens were left without post-curing. Half of the specimens from each subgroup were water-stored for 30 days while the other half was dry-stored (n=8). Flexural strength and flexural modulus was evaluated. Additional specimens were prepared and divided in the same way for surface hardness (n=96), and fracture toughness (n=96). Data were collected and analyzed with 1-way, 2-way ANOVA, and Tukey post-hoc analysis (α=.05).
Results: The post-curing method and storage conditions significantly affected all of the investigated mechanical properties (p < 0.05). The layer thickness significantly affected the flexural modulus (p < 0.01) and surface hardness (p = 0.07), however its effect on the fracture toughness was non-significant (p= 0.139). The specimens post-cured without the addition of nitrogen showed statistically significantly higher flexural strength, flexural modulus and fracture toughness than those post-cured with the addition of nitrogen (p < 0.05). However, the specimens post-cured with nitrogen showed significantly higher surface hardness than those without nitrogen (p < 0.05). Unpolymerized specimens showed the lowest values, which were significantly different from the other subgroups (p<0.05).
Conclusions: The post-curing method has a significant effect on the investigated biomechanical properties of 3D printed splint material.